Ford OBS 7.3 manual trans or 1998-2003 manual trans 4x4 for overlanding? F250 or F350

[Korben]

I'd be more then happy to trade you a V-belt setup for a serpentine setup, I'd rather have a serpentine.
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ATF is pretty commonly used in these engines for several things. First as an additive for the fuel to add some lubricity back to the ultra low sulfur diesel to make the injection pump(IP) last a lot longer. Secondly as fuel after working on the fuel system, like after replacing the fuel filter. ATF being a little thicker will pump/prime better to get it started. Any air in the IP messes it up until it can pump the air out, the thicker ATF helps with that. So when replacing the fuel filter fill it with ATF instead of diesel. EDIT- Be careful if you put ATF in the fuel, simply because ATF is dyed red, road diesel(taxed) has a green tint, farm/industrial diesel(untaxed) is dyed red. It's rare with pickups but cops can/do "dip" tanks to check to see if you have taxed diesel. However ATF can give your legal taxed diesel a red tint leading to a possible ticket.
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Edit, speaking of which air intrusion is one of the few things that will keep these suckers from running. Not only from running the tanks dry but there's a fuel return system that connects the fuel filter, IP, and each injector with small rubber hoses. This system leaking is a cause for many no start issues, often a leak won't leak fuel out but will leak air in, this air then get's into the IP and it can't pump. Many people remove the line to the fuel filter, it's unnecessary and without it air can't back track to the fuel filter(but air doesn't leave either) and thus the intake side of the IP. If your going to carry spare parts carry some of that hose, some spare O-rings for the injector caps, and maybe a spare injector cap or two. Another very good option is to add an electric fuel pump, stock there is only a mechanical lift pump, this pump can't pre-prime the fuel system and doesn't make much pressure. Adding an electric pump will both prime it before cranking but will put more pressure in the system, so for example if there is a leak in the return lines, it will push out diesel instead of let air in. Of course you then have a fuel leak, but that tells you where the leak is, and at least it runs.
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Me I kept the line on the filter and added an electric pump. One big reason for this is to deal with any air that does get in, either from running a tank too low or from some odd angle uncovering the fuel pickup. Having the electric pump and return line on the filter helps it push air out via the return, thus it recovers from air in the fuel system faster.

 

[underdrive]

The belt style swap is pretty involved, you basically have to replace EVERYTHING off the front of the engine sans the water pump. It's a bolt-off-bolt-on job, but it takes a while, and lots of parts. Not worth it IMHO unless you really really want V-belts. Thing about the V-belts is on these engines they will "slap" a lot especially at idle - alternator belt being the primary offender, and naturally this is also the rear-most belt and to replace it you have to remove the other three. You can add some idlers here and there to help with that, and if you run expensive belts (Gates for example) that seems to fix the issue.

The vacuum pump can seize up if it runs dry. There is a bolt on its back side, more or less inline with the pulley shaft - if you remove that bolt you can add some oil in there to keep the bearings and the cam and diaphragm plunger happy. Not sure what oil you're supposed to use, or even how much to put in, pretty sure ours got just regular 15/40 in it and we didn't pour in too much. Of course you only need to do if she's about to run dry, suppose there will be some goop around the shaft seal behind the pulley if that is the case?

You can offset the red ATF in the green fuel by dumping in some well-filtered dark-brown waste motor oil (WMO) from a gasoline engine, many people actually use that as a primary fuel. Or you can just not use ATF at all, and run some 2-cycle engine oil instead, IIRC there were some studies/test published online that showed that 2-cycle oil is better lubricant than ATF. Of course you can always run stuff that's specifically made for the job, like Diesel Kleen in the white bottle or Howe's or the Stanadyne additive.

Heads-up on the fuel pickup "shower heads" inside the tanks - those are made of some sort of rubber and with time will harden up and crack and sometimes fall off, which causes the pickup to suck fuel in not from the very bottom of the tank where the sump is but at much higher level, basically if you ever run out of fuel and your gauge still reads about 1/4" that's what happened. You can replace the shower head with another such part, or you can use a piece of 3/8" submersible fuel hose (SAE-30R10, good luck finding that locally, your best bet is a marina or a motorcycle shop) with a brass T-ee at the end - you hook the hose up to the middle leg of the T-ee, and then make the hose long enough for the T-ee to reach the bottom of the tank.

 

[Korben]

FWIW I really only talked about ATF as an additive cause it came up, but yeah these others are better lubricants. I personally don't like paying for oils to use as fuel additives, I use waste ATF and WMO a fair amount though.

 

[underdrive]

Actually I think it's good that you mentioned it - it was bound to come up sooner or later, especially with this "doomsday" type of engine that will run on just about anything that will burn

 

[jonb96150]

Thanks for all the great info! I've learned a lot from this thread. The best thing is that I ended up with an IDI engine and would not have had a clue about these trucks if it were not for you guys. With two tanks just putting along at low rpm I think the truck is going to have some serious backcountry range. With my LandCruiser (80 series gasser slushbox) I carry three jerry cans and it still is not enough. My Toyota BJ70 (4 cyl diesel w/ 5 sp) would get between 15 to 18 mpg off highway. I know a big ol truck with four more pistons won't get that but I'm eager to see what I can get.

I would go out and look at these fuel return lines right now but it snowed last night. Again, sigh. Oh well we need the water. A week ago we got 6". At least if melts fast this time of year.

The previous owner told me you could run the engine dry and it would prime itself. He didn't say that he had done that, but it was possible. Is that not the case, or would you run out of battery trying to prime with the mechanical lift pump?

I had forgotten about atf as a fuel conditioner, and wmo is intriguing. Didn't know about 2 cycle fuel additive, I think I'll try some of that.

 

[eggman918]

Some of my 4BT buddy's put a solid state electric pump right after the tank to use as a backup lift pump and to facilitate bleeding if needed a good one is ~$50.00.

 

[Korben]

It will prime itself without doing anything but yes you may run out of battery first if there is a total loss of prime and you don't do anything to help it a long, there is no manual prime built into these engines. Several simple things can be done to help it a long. The first of course is flooring the throttle so it pumps as much fuel/air as possible(usually this will be enough) Holding open the schrader valve on the fuel filter while cranking until fuel comes out. Removing the fuel filter and filling it with ATF or fuel. Unhooking the glow plug relay so they don't use up your battery, reconnect when any smoke(fuel vapor) comes out the exhaust. Loosening the lines at the injectors so air can escape. Taking the line between the tank and lift pump out of the equation by using a fuel jug and connecting it to the lift pump or adding an electric pump.
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Very unlikely you'll need to do much of the above, mostly for things like if the engine and tanks have been empty and sitting, a lot of work was done to the fuel system, or maybe of you let it idle until it stalled for lack of fuel.
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I mentioned disconnecting the glows, and you talk of being prepared, one thing you should absolutely do then is add a manual switch to the glow plug controller. To do two things, first to turn off the glow entirely so the controller doesn't glow automatically each time you turn the key on, useful to save the GPs and battery when working on the truck or it's already warmed up and you want to save battery. Secondly to allow you to manually turn on the glow if an issue arises that is preventing enough glow for it to fire. To do this you'll need to access the white wire connected at the glow plug relay/solenoid. White is a ground, stock turning on the ignition provides power to the red and the glow plug controller controls the whites path to ground. Easiest thing to do is to tap into the white and add a switch in it's path with it's own ground. Ideally a 6 terminal On/Off/Momentary On switch. On completes the pathway between relay and controller and it works like stock, off interrupts the pathway and the glows don't turn on, momentary completes it's own pathway to ground so key on and switch to momentary provides a manual glow, careful easy to over do it and damage the glow plugs.

 

[jonb96150]

Manual override for GPs'. Now on the list. It bugs me that the GPs' are hotted up every time I turn the ignition on, regardless of engine temp. My 98 turbo diesel Jetta GPs' barely light up with a warm engine. The Ford does not seem to sense temp, just a set time regardless of engine temp. One reason I use block heaters is to extend the life of GPs' but it does not seem to matter to the Ford. So this mod will be great! Previous owner must have had relay problems as he gave me a used one as a spare.


Inline aux electric fuel pump: Another good idea going on the list. I had done this to a gasser decades ago and spliced in a Tee with valve and hose and used it to gas up dirt bikes out in the boonies. Not much call to do this with a diesel, but since I'll be plumbing anyway it would be easy. While I'm at this is there a proven method of improving the tank vents so it does not take 5 minutes to get the last 3 gal of fuel in? I'm anal about mpg and the only way to get a true measurement is by filling to the point of visually seeing fuel in the filler hose.

Thanks again!

 

[Korben]

It bothers me as well that the glow system runs no matter how warm the engine is, but that's the small price you pay for rugged simplicity. The glow plug(GP) controller essentially only "reads" ignition signal and glow plug temperature, not engine or outside temps. So far I've done what I described above but there's a mod on my to do list that will get what you want and shouldn't be that hard. There's a temperature switch for the cold start fast idle and timing advance, I'm going to wire the glow plug controller to that switch.
http://repairguide.autozone.com/zne...96b43f/80/21/dd/2f/large/0996b43f8021dd2f.gif
Should be as simple as rerouting the RED/LT GN wire to the glow plug controller to get it's power from the GRY//RED wire between the temperature switch and the cold idle and cold advance solenoid. So when cold(can't remember the temp off the top of my head, want to say 175F) ignition power goes to the temp sensor then to the GP controller and is interrupted when hot. Ideally while in the process adding 3 more switches(have two already in my 90) each a manual override to turn on the GP controller, fast idle, and timing advance.
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I'm considering one other addition to this scheme as well, wiring so it glows constant while cranking no matter what anything else is doing. This would be tougher as it would require a couple relays.
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The mod in the previous post is all manual override to deal with issues, but the above mods would be automatic to minimize wait to start, glow, and crank time. No wait to start light or needed at all when engine coolant temp is over 175F IIRC. Glow on during cranking should minimize crank time, if it fires on the first rotation so be it, but if it doesn't having it glow should help it catch on the next. Voltage to the glows will be lower during cranking and you should never be cranking long enough to damage the GPs as you'll damage the starter as well.
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There's a lot on the net about the tank vents, I need to complete that research and do the work as well, but haven't yet so can't tell ya much off the top of my head.
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Edit - Been thinking about it, about adding the above to my rigs and adding a bit more redundancy. It's making me want to make a larger change that in the long run will work out better. I think instead of much of this wiring trickery to modify/override the stock GP solenoid I think I'll add another GP solenoid connected to the GPs in parallel. The first of the above mods to prevent it from glowing when hot would still need to be made to the stock wiring. But for both a manual glow and a glow during cranking use the second GP solenoid. This both simplifies the wiring but it provides a backup GP solenoid should the primary one fail.

 

[jonb96150]

Regarding the GP Controller, is this the correct white wire to interrupt with a switch? This is the spare I rec'd with the truck. The installed one also had that red paper tag. I could not read either of them except for "Caution" and the rest was illegible. That white wire terminal has a rubber cap on it as well. It does not go directly to chassis ground, but back into the bottom of the relay.

 

[Korben]

Regarding the GP Controller, is this the correct white wire to interrupt with a switch? This is the spare I rec'd with the truck. The installed one also had that red paper tag. I could not read either of them except for "Caution" and the rest was illegible. That white wire terminal has a rubber cap on it as well. It does not go directly to chassis ground, but back into the bottom of the relay.

Yes, it's tagged and covered to prevent accidental grounding which would leave the glows on whenever the ignition is on.

 

[jonb96150]

Thank you sir!

 

[jonb96150]

A bit of time has passed. It has been a busy 4 wheeling season here in the Sierra Nevada and the F250 has been just sitting. I took Korbens advice and bypassed the glow plug timer relay. It seems to work really good. I just interrupted the white wire on the GP relay, ran it to the dash with a momentary switch (have to keep it pushed in to complete the circuit, like a really old fashioned starting switch). The wait to start light on the dash still lights up and I just keep the switch pushed in until that timer light goes out. And if I don't push that switch the GP's will not glow up. So when the engine is warm the GP's don't get used at all, and I am in charge of how long the glow up when I need them. There is very little current going to the push button switch as it is just completing the ground so you don't need big wire.

Thanks again Korben!

Finally found a camper to put on top (2016 FWC Grandby) and I have to drive to Denver next week to pick it up and make a vacation out of it. So finally the F250 is going for a road trip!

Come this winter I will start on a few other mods suggested by the gurus who posted up. Thanks again!

 

[Regcabguy]

Im going to have to assume that you are referring to 1/2 ton (coil sprung) TTB

3/4 and 1-ton TTB front ends are leaf sprung.

There is ZERO benefit for a TTB over a solid axle.


Less flex, WORSE ride, and requires more maintenance than the solid axle.

I can vouch for that. My '86 F-250 4wd had the wandermatic TTB. My friend had an F-350 with the solid Dana 60. It tracked better and felt a dab stiffer offroad is all.

 

[Bella PSD]

That certainly depends upon the axle(s) you are talking about,
however actual strength differences based upon model is a moot subject due to the increased weight of the super duty.


But from research I did a long time ago... and Ill just assume the info is accurate (enough)
No guarantees though :sombrero:

OBS F250 has a TTB D50 load rating of 4600 lbs
SD F250 has a D50 solid axle load rating of 5000 lbs


OBS F350 has a ball joint non-unit bearing D60 load rating of 5000 lbs
SD F350 has a ball joint unit bearing D60 load rating of 5200 lbs

I read through all this and want to clear up one thing. The Super Duty from 99-03 are all the same from the F250-F350. Same brakes, same springs, axle, same everything. Coming off the assemble line Ford's Super Duty truck plant in Louisville and Mex simplified the process making the F250's the SAME as the F350 except for a larger rear block for the F350.

The early 98-99 Superduty's had a few things that changed soon after the launch but they were small changes: turbo up pipes and turbo wheel and a few other small changes.

One more thing to clear up is the cut off for the front Dana 50 axle to Dana 60 axle on all F250-F350 (remember they are basically the same truck) was right around build date of October 10th 2001. This was for the Louisville plant but the Mex plant was soon after as well but maybe not the 10/10/01 date.

A friend of mine had a 01 F350 with a build date of Oct. 1st+- a day or so and had the D50. I ordered an F350 back in the day and had a build date of Oct. 25th 2001 and got the Dana 60 plus ended up a 2002 not a 01.

I agree on the fact that the SD unit bearings suck when it comes time to replace. But I made it to 145K with stock unit bearings running 4.5” back space 16x10 and 35's then jumping up to 37's on heavy 3.5” bake space HMMWV beadlock rims. That's for the full life on the truck up to that mileage. Abuse on the stock unit bearings for sure but they still made it to 145,000 miles! I have since converted my stock 02 D60 unit bearings to Dynatrac free spin kit that mimics the OBS Ford F250-350 with serviceable heavy-duty parts.